The
secret of the Cooljag CJC66IC-A heatsink does not reveal itself until the fans' intake air reaches elevated temperatures, and
once that happens, the full speed of the fan kicks in and rapidly adds extra airflow to cool the
copper skived fins below.

With the aid of a thermistor sticking out the side of the fans' motor, the Everflow
fan can ramp up in speed from a whisper-quiet 1300RPM to a rather loud 6000RPM. At full blast, vibration can start
to be an issue.

The fully
copper skived heatsink features fins of 0.6mm
thickness, on a 2mm pitch, but what really makes the CoolJag CJC66IC-A stand out
is the copper base. Machined in four places are relief cuts which have removed
a 17mm x 26mm swath in each of the four corners. The reason for
this?

The cuts in the copper base not
only lighten the load of the entire 586g heatsink, but also help to promote
some airflow down into the area below the heatsink itself - further cooling
the processor below to some degree.

The 5mm thick copper base still
has enough material to fully contact the heatspreader of the Pentium 4
processor, and the cuts are unlikely to cause any structural
difficulties.